Systems and methods for current regulation in light-emitting-diode lighting systems

ABSTRACT

Systems and methods are provided herein for current regulation. An example system controller includes: a first controller terminal configured to receive an input voltage, the first controller terminal being further configured to allow a first current flowing into the system controller based at least in part on the input voltage in response to one or more switches being closed; a second controller terminal configured to allow the first current to flow out of the system controller through the second controller terminal in response to the one or more switches being closed; a fourth controller terminal coupled to the third controller terminal through a first capacitor, the first capacitor not being any part of the system controller; and an error amplifier configured to generate a compensation signal based at least in part on the current sensing signal, the error amplifier including a second capacitor.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201510581725.9, filed Sep. 14, 2015, incorporated by reference hereinfor all purposes.

2. BACKGROUND OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention providesystems and methods for current regulation. Merely by way of example,some embodiments of the invention have been applied tolight-emitting-diode lighting systems. But it would be recognized thatthe invention has a much broader range of applicability.

Light emitting diodes (LEDs) are widely used for lighting applications.FIG. 1 is a simplified diagram showing a conventional LED lightingsystem. The LED lighting system 100 includes a controller 102, resistors108, 116, 122, 124 and 128, capacitors 106, 110, 112 and 130, afull-wave rectifying component 104, diodes 114 and 118, an inductivecomponent 126 (e.g., an inductor), and a Zener diode 120. The controller102 includes terminals (e.g., pins) 138, 140, 142, 144, 146 and 148.

An alternate-current (AC) input voltage 150 is applied to the system100. The rectifying component 104 outputs a bulk voltage 152 (e.g., arectified voltage no smaller than 0 V) associated with the AC inputvoltage 150. The capacitor 112 (e.g., C3) is charged in response to thebulk voltage 152 through the resistor 108 (e.g., R1), and a voltage 154is provided to the controller 102 at the terminal 148 (e.g., terminalVDD). If the voltage 154 is larger than a threshold voltage (e.g., anunder-voltage lock-out threshold) in magnitude, the controller 102begins to operate, and a voltage associated with the terminal 148 (e.g.,terminal VDD) is clamped to a predetermined voltage. The terminal 138(e.g., terminal DRAIN) is connected to a drain terminal of an internalpower switch. The controller 102 outputs a drive signal (e.g., apulse-width-modulation signal) with a certain frequency and a certainduty cycle to close (e.g., turn on) or open (e.g., turn off) theinternal power switch so that the system 100 operates normally.

If the internal power switch is closed (e.g., being turned on), thecontroller 102 detects the current flowing through one or more LEDs 132through the resistor 122 (e.g., R2). Specifically, a voltage 156 on theresistor 122 (e.g., R2) is passed through the terminal 144 (e.g.,terminal CS) to the controller 102 for signal processing duringdifferent switching periods associated with the internal power switch.When the internal power switch is opened (e.g., being turned off) duringeach switching period is affected by peak magnitudes of the voltage 156on the resistor 122 (e.g., R2).

The inductive component 126 is connected with the resistors 124 and 128which generate a voltage 158. The controller 102 receives the voltage158 through the terminal 142 (e.g., terminal FB) for detection of ademagnetization process of the inductive component 126 to determine whenthe internal power switch is closed (e.g., being turned on). Thecapacitor 110 (e.g., C2) is connected to the terminal 140 (e.g.,terminal COMP) which is associated with an internal error amplifier. Thecapacitor 130 (e.g., C4) is configured to maintain an output voltage 158to keep stable current output for the one or more LEDs 132. A powersupply network including the resistor 116 (e.g., R5), the diode 118(e.g., D2) and the Zener diode 120 (e.g., ZD1) provides power supply tothe controller 102.

The LED lighting system 100 has some disadvantages. For example, thesystem 100 includes many components which may make it difficult toreduce bill of materials count (BOM) and achieve circuit minimizationand may cause a long start up time due to large current consumption.

Hence it is highly desirable to improve the techniques of currentregulation in LED lighting systems.

3. BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention providesystems and methods for current regulation. Merely by way of example,some embodiments of the invention have been applied tolight-emitting-diode lighting systems. But it would be recognized thatthe invention has a much broader range of applicability.

According to one embodiment, a system controller includes: a firstcontroller terminal configured to receive an input voltage, the firstcontroller terminal being further configured to allow a first currentflowing into the system controller based at least in part on the inputvoltage in response to one or more switches being closed; a secondcontroller terminal configured to allow the first current to flow out ofthe system controller through the second controller terminal in responseto the one or more switches being closed, the second controller terminalbeing further configured to receive a current sensing signal based atleast in part on the first current; and a third controller terminalconfigured to be biased at a first voltage. The system controllerfurther includes: a fourth controller terminal coupled to the thirdcontroller terminal through a first capacitor, the first capacitor notbeing any part of the system controller; an error amplifier configuredto generate a compensation signal based at least in part on the currentsensing signal, the error amplifier including a second capacitor; and adriver configured to generate a drive signal based at least in part onthe compensation signal and output the drive signal to affect the firstcurrent flowing from the first controller terminal to the secondcontroller terminal. The error amplifier further includes a first inputterminal, a second input terminal, and an output terminal. The firstinput terminal is coupled directly or indirectly with the secondcontroller terminal. The second input terminal is configured to receivea second voltage. The output terminal is coupled to the second capacitornot through any controller terminal.

According to another embodiment, a system controller is provided forregulating a current flowing from a first controller terminal to asecond controller terminal. The system controller includes: a low passfilter configured to receive a current sensing signal related to thecurrent flowing from the first controller terminal to the secondcontroller terminal, the low pass filter being further configured togenerate a filtered signal based at least in part on the current sensingsignal; an error amplifier configured to receive the filtered signal anda first reference signal and generate a compensation signal based atleast in part on the filtered signal and the first reference signal, theerror amplifier including a capacitor; and a driver configured togenerate a drive signal based on at least information associated withthe compensation signal and output the drive signal to one or moreswitches to affect the current flowing from the first controllerterminal to the second controller terminal. The error amplifier furtherincludes a first input terminal, a second input terminal, and an outputterminal. The first input terminal is configured to receive the filteredsignal. The second input terminal is configured to receive the referencesignal. The output terminal is coupled directly to the capacitor.

According to yet another embodiment, an error amplifier includes: atransconductance amplifier including a first input terminal and a secondinput terminal and a first output terminal, the first input terminalbeing configured to receive a first voltage signal, the second inputterminal being configured to receive a second voltage signal, the firstoutput terminal being configured to generate a current signal based atleast in part on the first voltage signal and the second voltage signal;a first switch including a first switch terminal and a second switchterminal and configured to be open or closed in response to a firstcontrol signal, the first switch terminal being coupled to the firstoutput terminal; a capacitor including a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupled tothe second switch terminal; an operational amplifier including a thirdinput terminal, a fourth input terminal, and a second output terminal,the third input terminal being coupled to the first capacitor terminal;and a second switch including a third switch terminal and a fourthswitch terminal, the third switch terminal being coupled to the secondoutput terminal, the fourth switch terminal being coupled to the firstoutput terminal, the second switch being configured to be open or closedin response to a second control signal. If the first control signal isat a first logic level, the second control signal is at a second logiclevel. If the first control signal is the second logic level, the secondcontrol signal is at the first logic level. The first logic level andthe second logic level are different.

In one embodiment, a system controller includes: a first controllerterminal configured to allow a first current to flow out of the systemcontroller through the first controller terminal to a resistorassociated with a resistance, the first controller terminal beingfurther configured to receive a voltage signal based at least in part onthe first current and the resistance, the resistor not being any part ofthe system controller. The system controller is configured to processthe received voltage signal, generate a clock signal associated with anoperating frequency based at least in part on the voltage signal, andchange the operating frequency based at least in part on the resistance.

In another embodiment, a system controller is provided for regulating acurrent flowing through one or more light emitting diodes. The systemcontroller includes: a voltage-to-current converter configured toreceive a first voltage associated with a first controller terminal andgenerate a first current based at least in part on the first voltage,the first controller terminal being configured to provide a secondcurrent to a resistor for generating the first voltage; an oscillatorconfigured to receive the first current and generate a clock signalbased at least in part on the first current, the clock signal beingassociated with an operating frequency of the system controller; and adriver configured to generate a drive signal associated with theoperating frequency and output the drive signal to affect a thirdcurrent flowing through one or more light emitting diodes. Theoscillator is further configured to generate a ramp signal associatedwith an operating frequency based at least in part on the first current,the operating frequency corresponding to an operating period, theoperating period including a ramp-up period and a ramp-down period. Theoscillator is further configured to: ramp up the ramp signal from afirst magnitude to a second magnitude during the ramp-up period and rampdown the ramp signal from the second magnitude to the first magnitudeduring the ramp-down period, the first magnitude and the secondmagnitude being different; and adjust a duration of the ramp-down periodin response to a change of the voltage signal in magnitude.

In yet another embodiment, a system controller is provided forregulating a current flowing through one or more light emitting diodes.The system controller includes: an error amplifier configured to receivea first voltage related to a first current flowing out of a firstcontroller terminal and generate a second voltage based at least in parton the first voltage; a clock-signal generator configured to receive thesecond voltage and generate a clock signal based at least in part on thesecond voltage, the clock signal being associated with an operatingfrequency of the system controller; and a driver configured to generatea drive signal associated with the operating frequency and output thedrive signal to affect a second current flowing through one or morelight emitting diodes. The system controller is further configured to:keep the operating frequency unchanged at a first frequency magnitude inresponse to the second voltage changing if the second voltage remainssmaller than a first voltage magnitude; keep the operating frequencyunchanged at a second frequency magnitude in response to the secondvoltage changing if the second voltage remains larger than a secondvoltage magnitude; and change the operating frequency in response to thesecond voltage changing if the second voltage remains larger than thefirst voltage magnitude and smaller than the second voltage magnitude.The second voltage magnitude is larger than the first voltage magnitude.

In yet another embodiment, a method is provided for regulating a currentflowing through one or more light emitting diodes. The method includes:receiving a first voltage related to a first current flowing out of afirst controller terminal; generating a second voltage based at least inpart on the first voltage; receiving the second voltage; generating aclock signal based at least in part on the second voltage, the clocksignal being associated with an operating frequency; generating a drivesignal associated with the operating frequency; and outputting the drivesignal to affect a second current flowing through one or more lightemitting diodes. Generating a clock signal based at least in part on thesecond voltage includes: keeping the operating frequency unchanged at afirst frequency magnitude in response to the second voltage changing ifthe second voltage remains smaller than a first voltage magnitude;keeping the operating frequency unchanged at a second frequencymagnitude in response to the second voltage changing if the secondvoltage remains larger than a second voltage magnitude; and changing theoperating frequency in response to the second voltage changing if thesecond voltage remains larger than the first voltage magnitude andsmaller than the second voltage magnitude. The second voltage magnitudeis larger than the first voltage magnitude.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram showing a conventional LED lightingsystem.

FIG. 2 is a simplified diagram showing an LED lighting system accordingto an embodiment of the present invention.

FIG. 3 is a simplified diagram showing a controller as part of the LEDlighting system as shown in FIG. 2 according to an embodiment of thepresent invention.

FIG. 4 is a simplified diagram showing certain components of thecontroller as part of the LED lighting system as shown in FIG. 2according to an embodiment of the present invention.

FIG. 5 is a simplified timing diagram for switching signals of thecontroller as part of the LED lighting system as shown in FIG. 4according to another embodiment of the present invention.

FIG. 6 is a simplified diagram showing an LED lighting system accordingto another embodiment of the present invention.

FIG. 7 is a simplified diagram showing a controller as part of the LEDlighting system as shown in FIG. 6 according to an embodiment of thepresent invention.

FIG. 8 is a simplified diagram showing certain components of the LEDlighting system as shown in FIG. 6 according to an embodiment of thepresent invention.

FIG. 9 is a simplified diagram showing an oscillator of a signalgenerator of the controller as part of the LED lighting system as shownin FIG. 8 according to an embodiment of the present invention.

FIG. 10 is a simplified timing diagram for the oscillator of the signalgenerator of the controller as part of the LED lighting system as shownin FIG. 8 according to an embodiment of the present invention.

FIG. 11 is a simplified diagram showing an LED lighting system accordingto yet another embodiment of the present invention.

FIG. 12 is a simplified diagram showing the controller as part of theLED lighting system as shown in FIG. 11 according to an embodiment ofthe present invention.

FIG. 13 is a simplified diagram showing a relationship between theoperating frequency of the LED lighting system as shown in FIG. 11 andan internal signal of the controller as part of the LED lighting systemaccording to an embodiment of the present invention.

FIG. 14 is a simplified diagram showing a signal generator of thecontroller as part of the LED lighting system as shown in FIG. 12according to an embodiment of the present invention.

FIG. 15 is a simplified diagram showing a relationship between aninternal current and an internal signal of the controller as shown inFIG. 12 as part of the LED lighting system according to an embodiment ofthe present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention providesystems and methods for current regulation. Merely by way of example,some embodiments of the invention have been applied tolight-emitting-diode lighting systems. But it would be recognized thatthe invention has a much broader range of applicability.

Referring back to FIG. 1, the AC input voltage 150 often has a frequencyof about 50 Hz or 60 Hz. A large compensation capacitor (e.g., with acapacitance of several hundred nF or even μF) is usually connected tothe terminal 140 (e.g., terminal COMP) to maintain the system stability,which may result in higher system costs and increase the volume of thesystem board.

FIG. 2 is a simplified diagram showing an LED lighting system accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. The LED lighting system 200 includes a controller202, resistors 208, 222, 224 and 228, capacitors 206, 212 and 230, afull-wave rectifying component 204, a diode 214, and an inductivecomponent 226 (e.g., an inductor). For example, the controller 202includes terminals 238, 242, 244, 246 and 248. In some embodiments, thecontroller 202 is located on a chip, and the terminals 238, 242, 244,246 and 248 correspond to different pins of the chip. As an example, theterminal 246 is biased to a chip ground voltage.

According to one embodiment, an alternate-current (AC) input voltage 250is applied to the system 200. For example, the rectifying component 204outputs a bulk voltage 252 (e.g., a rectified voltage no smaller than 0V) associated with the AC input voltage 250. In another example, thecapacitor 212 (e.g., C3) is charged in response to the bulk voltage 252through the resistor 208 (e.g., R1), and a voltage 254 is provided tothe controller 202 at the terminal 248 (e.g., terminal VDD). In yetanother example, if the voltage 254 is larger than a threshold voltage(e.g., an under-voltage lock-out threshold) in magnitude, the controller202 begins to operate, and a voltage associated with the terminal 248(e.g., terminal VDD) is clamped to a predetermined voltage. In yetanother example, the terminal 238 (e.g., terminal DRAIN) is connected toa drain terminal of an internal power switch. In yet another example,the controller 202 outputs a drive signal (e.g., apulse-width-modulation signal) with a certain frequency and a certainduty cycle to close (e.g., turn on) or open (e.g., turn off) theinternal power switch so that the system 200 operates normally.

According to another embodiment, if the internal power switch is closed(e.g., being turned on), the controller 202 detects the current flowingthrough one or more LEDs 232 through the resistor 222 (e.g., R2). Forexample, a sensing signal 256 generated on the resistor 222 (e.g., R2)is provided through the terminal 244 (e.g., terminal CS) to thecontroller 202 for signal processing during different switching periodsassociated with the internal power switch. In another example, when theinternal power switch is opened (e.g., being turned off) during eachswitching period is affected by peak magnitudes of the signal 256 on theresistor 222 (e.g., R2). In yet another example, the inductive component226 is connected with the resistors 224 and 228 which generate afeedback signal 258. In yet another example, the controller 202 receivesthe feedback signal 258 through the terminal 242 (e.g., terminal FB) fordetection of a demagnetization process of the inductive component 226 todetermine when the internal power switch is closed (e.g., being turnedon).

According to yet another embodiment, the controller 202 includes aninternal capacitor for compensation to achieve high power factor andhigh-precision constant LED current regulation. For example, theinternal capacitor is connected to an internal error amplifier forcompensation. As an example, the LED lighting system 200 can beimplemented to operate in a quasi-resonant (QR) mode or in adiscontinuous-conduction mode (DCM). In another example, the controller202 does not include a terminal COMP (e.g., a pin) and does not includean external compensation capacitor connected to such a terminal either,compared with the controller 102. In yet another example, the system 200does not include a power supply network (e.g., the network including theresistor 116 (e.g., R5), the diode 118 (e.g., D2) and the Zener diode120 (e.g., ZD1) as shown in FIG. 1).

FIG. 3 is a simplified diagram showing the controller 202 as part of theLED lighting system 200 according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. Thecontroller 202 includes a modulation component 312, an under-voltagelock-out (UVLO) component 302, a driver 314, a sensing component 310, aramping-signal generator 320, a low pass filter 318, an error amplifier316, a diode 306, a clamping component (e.g., a Zener diode) 304, andpower switches 308 and 322. For example, the power switches 308 and 322each include a transistor. In another example, the power switch 308includes a metal-oxide-semiconductor field-effect transistor (MOSFET).In yet another example, the power switch 322 includes a MOSFET.

According to one embodiment, the terminal 248 (e.g., terminal VDD) isconnected to a gate terminal of the switch 308 and the UVLO component302 detects the voltage 254. For example, if the voltage 254 is largerthan a predetermined threshold (e.g., a UVLO threshold) in magnitude,the controller 202 begins to operate. In another example, the sensingcomponent 310 detects, through the terminal 242 (e.g., terminal FB), thefeedback signal 258 to determine whether the demagnetization processassociated with the inductive component 226 has completed and outputs asignal 330. In yet another example, the sensing component 310 determineswhether the output voltage 258 exceeds a threshold so as to trigger anover-voltage mechanism.

According to another embodiment, the error amplifier 316 detects,through the terminal 244 (e.g., terminal CS), an output current 260flowing through the one or more LEDs 232. For example, the low passfilter 318 receives the sensing signal 256 and outputs a signal 326 tothe error amplifier 316 which also receives a reference signal 328. Inanother example, the error amplifier 316 outputs a signal 388 (e.g.,V_(c)) to the modulation component 312 which also receives the signal330 from the sensing component 310 and a ramp signal 324 from theramping-signal generator 320. In yet another example, the modulationcomponent 312 outputs a modulation signal 332 to the driver 314 whichoutputs a drive signal 334 to the switch 322 (e.g., at the gateterminal). In some embodiments, current consumption of the system 200 isreduced to a low magnitude with the operation of the controller 202,which may result in a fast start-up process. In certain embodiments, theerror amplifier 316 is not connected directly to any controller terminal(e.g., any pin on a chip).

FIG. 4 is a simplified diagram showing certain components of thecontroller 202 as part of the LED lighting system 200 according to anembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications. The low pass filter 318 includes a RC filter containing aresistor 402 and a capacitor 404. For example, the error amplifier 316includes a transconductance amplifier 406, resistors 408 and 416,switches 410 and 412, an operational amplifier 414, and a capacitor 418.In another example, the error amplifier 316 does not include theresistor 416.

According to one embodiment, the low pass filter 318 is configured tofilter out the high frequency components of the signal 324 and outputsthe signal 326 to the transconductance amplifier 406 (e.g., at theinverting input terminal, “−”). For example, the switch 410 (e.g., SW1)is connected between an output terminal of the transconductanceamplifier 406 and the resistor 416 (e.g., R2). In another example, theresistor 416 is connected to the capacitor 418 (e.g., C2) which isconnected to the operational amplifier 414 (e.g., at the non-invertinginput terminal, “+”). In yet another example, the switch 412 (e.g., SW2)is connected between an output terminal of the operational amplifier 414and the resistor 408 which is connected to the output terminal of thetransconductance amplifier 406. In yet another example, the outputterminal of the operational amplifier 414 is connected to its invertinginput terminal, “−”. In some embodiments, the capacitor 418 includesterminals 490 and 492. For example, the terminal 490 is not connecteddirectly to any controller terminal (e.g., any pin on a chip).

According to another embodiment, the switch 410 (e.g., SW1) and theswitch 412 (e.g., SW2) operate in response to a switching signal 420(e.g., K1) and a switching signal 422 (e.g., K2), respectively. Forexample, the switching signal 420 (e.g., K1) and the switching signal422 (e.g., K2) are complementary logic signals. In another example, theswitching signal 420 (e.g., K1) and the switching signal 422 (e.g., K2)are clock signals generated by the controller 202, both corresponding toa same frequency.

FIG. 5 is a simplified timing diagram for the switching signals 420 and422 of the controller 202 as part of the LED lighting system 200according to another embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 502 representsthe switching signal 420 (e.g., K1) as a function of time, and thewaveform 504 represents the switching signal 422 (e.g., K2) as afunction of time.

According to one embodiment, during a first time period (e.g., T₁), theswitching signal 420 (e.g., K1) is at a logic high level, and theswitching signal 422 (e.g., K2) is at a logic low level. For example,during a second time period (e.g., T₂), the switching signal 422 is at alogic high level, and the switching signal 420 is at a logic low level.

Referring to FIG. 4 and FIG. 5, if the switching signal 420 (e.g., K1)is at the logic high level during a particular time period (e.g., T₁),then the switch 410 (e.g., SW1) is closed (e.g., being turned on),according to some embodiments. For example, the transconductanceamplifier 406 outputs the signal 424 for charging/discharging thecapacitor 418 (e.g., C2). As an example, the signal 388 is provided tothe modulation component 312 to affect an on-time period during whichthe switch 322 is closed (e.g., being turned on).

According to certain embodiments, if the switching signal 420 (e.g., K1)is at the logic low level during another time period (e.g., T₂), thenthe switch 410 (e.g., SW1) is opened (e.g., being turned off). Forexample, the transconductance amplifier 406 is not connected to thecapacitor 418 (e.g., C2), and the signal 388 associated with thecapacitor 418 (e.g., C2) keeps at a magnitude before the switch 410(e.g., SW1) is opened. In some embodiments, if the system 200 operatesfor a long period of time, the effective transconductance of the erroramplifier 316 is determined as follows:

GM=D×g _(m)   (Equation 1)

where D represents a duty cycle associated with the switch 410 (e.g.,SW1), and g_(m) represents the transconductance of the transconductanceamplifier 406. For example, if the duty cycle associated with the switch410 is far less than 1, the effective transconductance of the erroramplifier 316 is reduced (e.g., proportionally), and correspondingly thecapacitor 418 may have a smaller capacitance.

According to one embodiment, if the switching signal 420 (e.g., K1) isat the logic low level during another time period (e.g., T₂), theswitching signal 422 (e.g., K2) is at the logic high level and theswitch 412 (e.g., SW2) is closed (e.g., being turned on). For example,the signal 424 is clamped to be equal in magnitude to the signal 388(e.g., the voltage on the capacitor 418, C2), considering thecharacteristics of the operational amplifier 414 which may serve as abuffer, so as to maintain the output of the transconductance amplifier406 in a normal operation range. As an example, transient effects fromthe changes of the switching signal 420 (e.g., K1) are suppressedthrough proper measures.

As discussed above and further emphasized here, FIGS. 2, 3, 4 and 5 aremerely examples, which should not unduly limit the scope of the claims.One of ordinary skill in the art would recognize many variations,alternatives, and modifications. For example, the controller 202 asshown in FIG. 3 and FIG. 4 can be implemented as part of the LEDlighting system 200 which operates in a quasi-resonant (QR) mode or in adiscontinuous-conduction mode (DCM).

FIG. 6 is a simplified diagram showing an LED lighting system accordingto another embodiment of the present invention. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications. The LED lighting system 600 includes acontroller 602, resistors 608, 610, 622, 624 and 628, capacitors 606,612 and 630, a full-wave rectifying component 604, a diode 614, and aninductive component 626 (e.g., an inductor). For example, the controller602 includes terminals (e.g., pins) 638, 640, 642, 644, 646 and 648. Insome embodiments, the controller 602 is located on a chip, and theterminals 638, 642, 644, 646 and 648 correspond to different pins of thechip. As an example, the terminal 646 is biased to a chip groundvoltage. As another example, the terminals 638, 642, 644, 646 and 648are the same as the terminals 238, 242, 244, 246 and 248.

The system 600 adjusts an operating frequency through one or moreexternal components (e.g., the resistor 610) connected to the terminal640 (e.g., terminal Fset), according to some embodiments. For example,an alternate-current (AC) input voltage 650 is applied to the system600. As an example, the rectifying component 604 outputs a bulk voltage652 (e.g., a rectified voltage no smaller than 0 V) associated with theAC input voltage 650. In another example, the capacitor 612 (e.g., C3)is charged in response to the bulk voltage 652 through the resistor 608(e.g., R1), and a voltage 654 is provided to the controller 602 at theterminal 648 (e.g., terminal VDD). In yet another example, if thevoltage 654 is larger than a threshold voltage (e.g., an under-voltagelock-out threshold) in magnitude, the controller 602 begins to operate,and a voltage associated with the terminal 648 (e.g., terminal VDD) isclamped to a predetermined voltage. In yet another example, the terminal638 (e.g., terminal DRAIN) is connected to a drain terminal of aninternal power switch. In yet another example, the controller 602outputs a drive signal (e.g., a pulse-width-modulation signal) with acertain frequency and a certain duty cycle to close (e.g., turn on) oropen (e.g., turn off) the internal power switch so that the system 600operates normally.

According to another embodiment, if the internal power switch is closed(e.g., being turned on), the controller 602 detects the current flowingthrough one or more LEDs 632 through the resistor 622 (e.g., R2). Forexample, a sensing signal 656 generated on the resistor 622 (e.g., R2)is provided through the terminal 644 (e.g., terminal CS) to thecontroller 602 for signal processing during different switching periodsassociated with the internal power switch. In another example, when theinternal power switch is opened (e.g., being turned off) during eachswitching period is affected by peak magnitudes of the signal 656 on theresistor 622 (e.g., R2). In yet another example, the inductive component626 is connected with the resistors 624 and 628 which generate afeedback signal 658. In yet another example, the controller 602 receivesthe feedback signal 658 through the terminal 642 (e.g., terminal FB) fordetection of a demagnetization process of the inductive component 626 todetermine when the internal power switch is closed (e.g., being turnedon).

According to yet another embodiment, the controller 602 includes aninternal capacitor for compensation to achieve high power factor andhigh-precision constant LED current regulation. For example, theinternal capacitor is connected to an internal error amplifier forcompensation. As an example, the LED lighting system 600 can beimplemented to operate in a quasi-resonant (QR) mode or in adiscontinuous-conduction mode (DCM). In another example, the controller602 does not include a terminal COMP (e.g., a pin) and does not includean external compensation capacitor connected to such a terminal either,compared with the controller 102. In yet another example, the system 600does not include a power supply network (e.g., the network including theresistor 116 (e.g., R5), the diode 118 (e.g., D2) and the Zener diode120 (e.g., ZD1) as shown in FIG. 1).

According to yet another embodiment, a current 690 flows through theterminal 640 (e.g., terminal Fset) and a voltage 688 is generated by theresistor 610 in response to the current 690. For example, the current690 flows from the terminal 640 toward the resistor 610. In anotherexample, the current 690 flows from the resistor 610 toward the terminal640. In yet another example, the controller 602 generates an internalclock signal using the voltage 688, and the operating frequency of thesystem 600 is related to the internal clock signal. In some embodiments,the resistance of the resistor 610 is changed so that the voltage 688 ischanged to affect the operating frequency of the system 600.

FIG. 7 is a simplified diagram showing the controller 602 as part of theLED lighting system 600 according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. Thecontroller 602 includes a modulation component 712, an under-voltagelock-out (UVLO) component 702, a driver 714, a sensing component 710, asignal generator 720, a low pass filter 718, an error amplifier 716, adiode 706, a Zener diode 704, and power switches 708 and 722. Forexample, the power switches 708 and 722 each include a transistor. Inanother example, the power switch 708 includes ametal-oxide-semiconductor field-effect transistor (MOSFET). In yetanother example, the power switch 722 includes a MOSFET.

In some embodiments, the error amplifier 716 is the same as the erroramplifier 316. In certain embodiments, the low pass filter 718 is thesame as the low pass filter 318. In particular embodiments, the driver714 is the same as the driver 314.

According to one embodiment, the terminal 648 (e.g., terminal VDD) isconnected to a gate terminal of the switch 708 and the UVLO component702 detects the voltage 754. For example, if the voltage 754 is largerthan a predetermined threshold (e.g., a UVLO threshold) in magnitude,the controller 602 begins to operate. In another example, the sensingcomponent 710 detects, through the terminal 642 (e.g., terminal FB), thefeedback signal 658 to determine whether the demagnetization processassociated with the inductive component 626 has completed and outputs asignal 730. In yet another example, the sensing component 710 determineswhether the output voltage 658 exceeds a threshold so as to trigger anover-voltage mechanism.

According to another embodiment, the error amplifier 716 detects,through the terminal 644 (e.g., terminal CS), an output current 660flowing through the one or more LEDs 632. For example, the low passfilter 718 receives the sensing signal 656 and outputs a signal 726 tothe error amplifier 716 which also receives a reference signal 728. Inanother example, the error amplifier 716 outputs a signal 788 (e.g.,V_(c)) to the modulation component 712 which also receives the signal730 from the sensing component 710. In yet another example, themodulation component 712 receives a clock signal 725 and a ramp signal724 from the signal generator 720 which receives the voltage 688 throughthe terminal 640 (e.g., terminal Fset). In yet another example, themodulation component 712 outputs a modulation signal 732 to the driver714 which outputs a drive signal 734 to the switch 722 (e.g., at thegate terminal). As an example, the clock signal 725 and the ramp signal724 are of a same frequency related to the operating frequency of thesystem 600 which corresponds to an operational period. As anotherexample, the operational period includes a ramp-up period and aramp-down period. As yet another example, the ramp signal ramps up froma first magnitude to a second magnitude during the ramp-up period andramps down from the second magnitude to the first magnitude during theramp-down period, the first magnitude and the second magnitude beingdifferent. In some embodiments, current consumption of the system 600 isreduced to a low magnitude with the operation of the controller 602,which may result in a fast start-up process.

FIG. 8 is a simplified diagram showing certain components of the LEDlighting system 600 according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. The signal generator720 includes a voltage-to-current converter 802 and an oscillator 804.

According to one embodiment, the current 690 (e.g., generated by acurrent source component 860) flows through the terminal 640 (e.g.,terminal Fset) to generate the voltage 688 and has a predeterminedmagnitude. For example, the current 690 flows from the terminal 640toward the resistor 610. In another example, the current 690 flows fromthe resistor 610 toward the terminal 640. In yet another example, theconverter 802 generates a current 808 (e.g., I_(c)) based on the voltage688. In yet another example, the oscillator 804 receives the current 808and a reference current 806 (e.g., I₀ ) and outputs the ramp signal 724and the clock signal 725. As an example, the clock signal 725 and theramp signal 724 are of a same frequency. In another example, thereference current 806 has a predetermined magnitude.

FIG. 9 is a simplified diagram showing the oscillator 804 of the signalgenerator 720 of the controller 602 as part of the LED lighting system600 according to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The oscillator 804 includesa comparator 902, a NOT gate 904, switches 908, 912 and 918, and acapacitor 916.

According to one embodiment, the switch 918 is connected to thecomparator 902 (e.g., at the non-inverting input terminal, “+”), and thecapacitor 916 is connected to the comparator 902 (e.g., at the invertinginput terminal, “−”). For example, a charge current 906 (e.g., generatedby a current sink component 960) flows through the switch 908 if theswitch 908 is closed (e.g., being turned on) to charge the capacitor 916to generate the ramp signal 724 which is received by the comparator 902(e.g., at the inverting input terminal, “−”). In another example, theswitches 908 and 912 are controlled by switching signals 910 and 914,respectively. In yet another example, the switching signals 910 and 914are complementary to each other (e.g., as shown in FIG. 10). In yetanother example, the switch 918 is controlled by a switching signal 920.As an example, if the switching signal 920 is at the logic high level,in response the switch 918 passes a voltage 924 (e.g., VH) to thecomparator 902 (e.g., at the non-inverting terminal, “+”). As anotherexample, if the switching signal 920 is at the logic low level, inresponse the switch 918 passes a voltage 926 (e.g., VL) to thecomparator 902 (e.g., at the non-inverting terminal, “+”). As yetanother example, the comparator 902 outputs the switching signal 910which is the same as the clock signal 725. As yet another example, theNOT gate 904 outputs the switching signal 914.

FIG. 10 is a simplified timing diagram for the oscillator 804 of thesignal generator 720 of the controller 602 as part of the LED lightingsystem 600 according to an embodiment of the present invention. Thisdiagram is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 980 representsthe ramp signal 724 as a function of time, the waveform 982 representsthe switching signal 910 (e.g., K1 as a function of time, and thewaveform 984 represents the switching signal 914 (e.g., K2) as afunction of time.

According to one embodiment, at time t₀, the oscillator 804 begins tooperate, and the switch 918 passes the voltage 924 (e.g., VH) to thecomparator 902. For example, between the time t₀ and time t₁, theswitching signal 910 (e.g., K1) is at the logic high level (e.g., asshown by the waveform 982), and in response the switch 908 is closed(e.g., being turned on). In another example, the switching signal 914(e.g., K2) is at the logic low level (e.g., as shown by the waveform984), and in response the switch 912 is open (e.g., being turned off).In yet another example, the capacitor 916 is charged in response to thecurrent 906 which flows through the switch 908. In yet another example,between the time t₀ and the time t₁, the ramp signal 724 increases(e.g., linearly) in magnitude over time (e.g., as shown by the waveform980).

According to another embodiment, if the ramp signal 724 increases tobecome larger than the voltage 924 (e.g., VH) in magnitude (e.g., at thetime t₁), the switching signal 910 (e.g., K1) changes to the logic lowlevel (e.g., as shown by the waveform 982), and in response the switch908 is opened (e.g., being turned off). For example, the switchingsignal 914 (e.g., K2) changes to the logic high level (e.g., at the timet₁ as shown by the waveform 984), and in response the switch 912 isclosed (e.g., being turned on). In another example, the switch 918passes the voltage 926 (e.g., VL) to the comparator 902. In yet anotherexample, the capacitor 916 begins to be discharged based at least inpart on the current 808 (e.g., I_(c)) and the current 806 (e.g., I₀). Asan example, the current 808 (e.g., I_(c)) is generated by a current sinkcomponent 962, and the current 806 (e.g., I₀) is generated by a currentsink component 964. As another example, between the time t₁ and time t₂,the switching signal 910 (e.g., K1) remains at the logic low level(e.g., as shown by the waveform 982), and the switching signal 914(e.g., K2) remains at the logic high level (e.g., as shown by thewaveform 984). In yet another example, the ramp signal 724 decreases(e.g., linearly) in magnitude.

According to yet another example, if the ramp signal 724 decreases tobecome smaller than the voltage 926 (e.g., VL) in magnitude (e.g., atthe time t₂), the switching signal 910 (e.g., K1) changes to the logichigh level (e.g., as shown by the waveform 982), and in response theswitch 908 is closed (e.g., being turned on). For example, the switchingsignal 914 (e.g., K2) changes to the logic low level (e.g., as shown bythe waveform 984), and in response the switch 912 is opened (e.g., beingturned off). In another example, the switch 918 passes the voltage 926(e.g., VH) to the comparator 902. In yet another example, the capacitor916 begins to be charged in response to the current 906 that flowsthrough the switch 908 again.

According to some embodiments, if the resistance of the resistor 610 ischanged, the voltage 688 changes in magnitude, and in response thecurrent 808 (e.g., I_(c)) changes in magnitude, which may change theduration of charging/discharging the capacitor 916 and thus theoperating frequency of the system 600. For example, if the current 808(e.g., I_(c)) decreases in magnitude, the duration of discharging thecapacitor 916 increases (e.g., from T1 to T2 as shown in FIG. 10). Thesmaller the magnitude of the current 808 (e.g., I_(c)), the larger theduration of discharging the capacitor 916 (e.g., further increasing toT3 or T4 as shown in FIG. 10), according to certain embodiments. Thelarger the duration of discharging the capacitor 916, the smaller theoperating frequency of the system 600, according to some embodiments.

As discussed above and further emphasized here, FIGS. 6-10 are merelyexamples, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, FIG. 6 is implemented together with FIG.2. In another example, FIG. 3, FIG. 4, and/or FIG. 5 are implemented,individually or in combination, as at least one or more parts of thecontroller 602 as shown in FIG. 6.

Also, as discussed above and further emphasized here, FIGS. 2-5 aremerely examples, which should not unduly limit the scope of the claims.One of ordinary skill in the art would recognize many variations,alternatives, and modifications. For example, an LED lighting system(e.g., operating in a DCM mode) can be configured to change an operatingfrequency with an output of an internal error amplifier, instead ofhaving a fixed operating frequency.

FIG. 11 is a simplified diagram showing an LED lighting system accordingto yet another embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The LED lighting system1100 includes a controller 1102, resistors 1108, 1122, 1124 and 1128,capacitors 1106, 1112 and 1130, a full-wave rectifying component 1104, adiode 1114, and an inductive component 1126 (e.g., an inductor). Forexample, the controller 1102 includes terminals 1138, 1142, 1144, 1146and 1148. As an example, the controller 1102, the resistors 1108, 1122,1124 and 1128, the capacitors 1106, 1112 and 1130, the full-waverectifying component 1104, the diode 1114, and the inductive component1126 are the same as the controller 202, the resistors 208, 222, 224 and228, the capacitors 206, 212 and 230, the full-wave rectifying component204, the diode 214, and the inductive component 226, respectively. Insome embodiments, the controller 1102 is located on a chip, and theterminals 1138, 1142, 1144, 1146 and 1148 correspond to different pinsof the chip. As an example, the terminal 1146 is biased to a chip groundvoltage.

According to one embodiment, an alternate-current (AC) input voltage1150 is applied to the system 1100. For example, the rectifyingcomponent 1104 outputs a bulk voltage 1152 (e.g., a rectified voltage nosmaller than 0 V) associated with the AC input voltage 1150. In anotherexample, the capacitor 1112 (e.g., C3) is charged in response to thebulk voltage 1152 through the resistor 1108 (e.g., R1), and a voltage1154 is provided to the controller 1102 at the terminal 1148 (e.g.,terminal VDD). In yet another example, if the voltage 1154 is largerthan a threshold voltage (e.g., an under-voltage lock-out threshold) inmagnitude, the controller 1102 begins to operate, and a voltageassociated with the terminal 1148 (e.g., terminal VDD) is clamped to apredetermined voltage. In yet another example, the terminal 1138 (e.g.,terminal DRAIN) is connected to a drain terminal of an internal powerswitch. In yet another example, the controller 1102 outputs a drivesignal (e.g., a pulse-width-modulation signal) with a certain frequencyand a certain duty cycle to close (e.g., turn on) or open (e.g., turnoff) the internal power switch so that the system 1100 operatesnormally.

According to another embodiment, if the internal power switch is closed(e.g., being turned on), the controller 1102 detects the current flowingthrough one or more LEDs 1132 through the resistor 1122 (e.g., R2). Forexample, a sensing signal 1156 generated on the resistor 1122 (e.g., R2)is provided through the terminal 1144 (e.g., terminal CS) to thecontroller 1102 for signal processing during different switching periodsassociated with the internal power switch. In another example, when theinternal power switch is opened (e.g., being turned off) during eachswitching period is affected by peak magnitudes of the signal 1156 onthe resistor 1122 (e.g., R2). In yet another example, the inductivecomponent 1126 is connected with the resistors 1124 and 1128 whichgenerate a feedback signal 1158. In yet another example, the controller1102 receives the feedback signal 1158 through the terminal 1142 (e.g.,terminal FB) for detection of a demagnetization process of the inductivecomponent 1126 to determine when the internal power switch is closed(e.g., being turned on).

According to yet another embodiment, the controller 1102 includes aninternal capacitor for compensation to achieve high power factor andhigh-precision constant LED current regulation. For example, theinternal capacitor is connected to an internal error amplifier forcompensation. In another example, the operating frequency of the system1100 changes with the output of the internal error amplifier. In yetanother example, the smaller in magnitude the output of the internalerror amplifier, the smaller in magnitude the operating frequency of thesystem 1100. As an example, the LED lighting system 1100 can beimplemented to operate in a DCM or QR mode. In another example, thecontroller 1102 does not include a terminal COMP (e.g., a pin) and doesnot include an external compensation capacitor connected to such aterminal either, compared with the controller 102. In yet anotherexample, the system 1100 does not include a power supply network (e.g.,the network including the resistor 116 (e.g., R5), the diode 118 (e.g.,D2) and the Zener diode 120 (e.g., ZD1) as shown in FIG. 1).

FIG. 12 is a simplified diagram showing the controller 1102 as part ofthe LED lighting system 1100 according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. Thecontroller 1102 includes a modulation component 1212, an UVLO component1202, a driver 1214, a sensing component 1210, a signal generator 1220,a low pass filter 1218, an error amplifier 1216, a diode 1206, a Zenerdiode 1204, and power switches 1208 and 1222. For example, the powerswitches 1208 and 1222 each include a transistor. In another example,the power switch 1208 includes a metal-oxide-semiconductor field-effecttransistor (MOSFET). In yet another example, the power switch 1222includes a MOSFET.

In some embodiments, the error amplifier 1216 is the same as the erroramplifier 316. In certain embodiments, the low pass filter 1218 is thesame as the low pass filter 318. In some embodiments, the driver 1214 isthe same as the driver 314. In particular embodiments, the erroramplifier 1216 is the same as the error amplifier 716. In certainembodiments, the low pass filter 1218 is the same as the low pass filter718. In some embodiments, the modulation component 1212 is the same asthe modulation component 712. In certain embodiments, the driver 1214 isthe same as the driver 714.

According to one embodiment, the terminal 1148 (e.g., terminal VDD) isconnected to a gate terminal of the switch 1208 and the UVLO component1202 detects the voltage 1254. For example, if the voltage 1254 islarger than a predetermined threshold (e.g., a UVLO threshold) inmagnitude, the controller 1102 begins to operate. In another example,the sensing component 1210 detects, through the terminal 1142 (e.g.,terminal FB), the feedback signal 1158 to determine whether thedemagnetization process associated with the inductive component 1126 hascompleted and outputs a signal 1230. In yet another example, the sensingcomponent 1210 determines whether the output voltage 1158 exceeds athreshold so as to trigger an over-voltage mechanism.

According to another embodiment, the error amplifier 1216 detects,through the terminal 1144 (e.g., terminal CS), an output current 1160flowing through the one or more LEDs 1132. For example, the low passfilter 1218 receives the sensing signal 1156 and outputs a signal 1226to the error amplifier 1216 which also receives a reference signal 1228.In another example, the error amplifier 1216 outputs a signal 1288(e.g., Vc) to the modulation component 1212 which also receives thesignal 1230 from the sensing component 1210. In yet another example, themodulation component 1212 receives a clock signal 1225 and a ramp signal1224 from the signal generator 1220 which receives the signal 1288(e.g., V_(c)). In yet another example, the modulation component 1212outputs a modulation signal 1232 to the driver 1214 which outputs adrive signal 1234 to the switch 1222 (e.g., at the gate terminal). As anexample, the clock signal 1225 and the ramp signal 1224 are of a samefrequency related to the operating frequency of the system 1100. In someembodiments, current consumption of the system 1100 is reduced to a lowmagnitude with the operation of the controller 1102, which may result ina fast start-up process.

FIG. 13 is a simplified diagram showing a relationship between theoperating frequency of the system 1100 and the signal 1288 of thecontroller 1102 as part of the LED lighting system 1100 according to anembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications.

According to one embodiment, if the signal 1288 (e.g., V_(c)) is smallerin magnitude than a first voltage (e.g., V1), the operating frequency ofthe system 1100 keeps at a magnitude 1304. For example, if the signal1288 (e.g., V_(c)) is larger in magnitude than a second voltage (e.g.,V2), the operating frequency of the system 1100 keeps at a magnitude1302. In another example, if the signal 1288 (e.g., V_(c)) is smaller inmagnitude than the second voltage (e.g., V2) and larger in magnitudethan the first voltage (e.g., V1), the operating frequency of the system1100 changes with the signal 1288 (e.g., V_(c)). As an example, if thesignal 1288 (e.g., V_(c)) is smaller in magnitude than the secondvoltage (e.g., V2) and larger in magnitude than the first voltage (e.g.,V1), the operating frequency of the system 1100 increases (e.g.,linearly or non-linearly) with the increasing signal 1288 (e.g., V_(c)).

FIG. 14 is a simplified diagram showing the signal generator 1220 of thecontroller 1102 as part of the LED lighting system 1100 according to anembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications. The signal generator 1220 includes a voltage-to-currentconverter 1302 and an oscillator 1304.

According to one embodiment, the converter 1302 receives the signal 1288(e.g., V_(c)) and generates a current 1308 (e.g., I_(c)). For example,the oscillator 1304 receives the current 1308 and a reference current1306 (e.g., I0) and outputs the ramp signal 1224 and the clock signal1225. As an example, the clock signal 1225 and the ramp signal 1224 areof a same frequency. In another example, the reference current 1306 hasa predetermined magnitude.

FIG. 15 is a simplified diagram showing a relationship between thecurrent 1308 (e.g., I_(c)) and the signal 1288 of the controller 1102 aspart of the LED lighting system 1100 according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications.

According to one embodiment, if the signal 1288 (e.g., V_(c)) is smallerin magnitude than a first voltage (e.g., V1), the current 1308 (e.g.,I_(c)) keeps at a magnitude 1504. For example, if the signal 1288 (e.g.,V_(c)) is larger in magnitude than a second voltage (e.g., V2), thecurrent 1308 (e.g., I_(c)) keeps at a magnitude 1502. In anotherexample, if the signal 1288 (e.g., V_(c)) is smaller in magnitude thanthe second voltage (e.g., V2) and larger in magnitude than the firstvoltage (e.g., V1), the current 1308 (e.g., I_(c)) changes with thesignal 1288 (e.g., V_(c)). As an example, if the signal 1288 (e.g.,V_(c)) is smaller in magnitude than the second voltage (e.g., V2) andlarger in magnitude than the first voltage (e.g., V1), the current 1308(e.g., I_(c)) increases (e.g., linearly or non-linearly) with theincreasing signal 1288 (e.g., V_(c)).

As discussed above and further emphasized here, FIGS. 11-15 are merelyexamples, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In one embodiment, FIG. 11 is implemented togetherwith FIG. 2. For example, FIG. 3, FIG. 4, and/or FIG. 5 are implemented,individually or in combination, as at least one or more parts of thecontroller 1102 as shown in FIG. 11.

In another embodiment, FIG. 11 is implemented together with FIG. 6. Forexample, FIG. 7, FIG. 8, FIG. 9, and/or FIG. 10 are implemented,individually or in combination, as at least one or more parts of thecontroller 1102 as shown in FIG. 11. In yet another embodiment, FIG. 11is implemented together with both FIG. 2 and FIG. 6. For example, FIG.3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, and/or FIG. 10 areimplemented, individually or in combination, as at least one or moreparts of the controller 1102 as shown in FIG. 11.

According to another embodiment, a system controller includes: a firstcontroller terminal configured to receive an input voltage, the firstcontroller terminal being further configured to allow a first currentflowing into the system controller based at least in part on the inputvoltage in response to one or more switches being closed; a secondcontroller terminal configured to allow the first current to flow out ofthe system controller through the second controller terminal in responseto the one or more switches being closed, the second controller terminalbeing further configured to receive a current sensing signal based atleast in part on the first current; and a third controller terminalconfigured to be biased at a first voltage. The system controllerfurther includes: a fourth controller terminal coupled to the thirdcontroller terminal through a first capacitor, the first capacitor notbeing any part of the system controller; an error amplifier configuredto generate a compensation signal based at least in part on the currentsensing signal, the error amplifier including a second capacitor; and adriver configured to generate a drive signal based at least in part onthe compensation signal and output the drive signal to affect the firstcurrent flowing from the first controller terminal to the secondcontroller terminal. The error amplifier further includes a first inputterminal, a second input terminal, and an output terminal. The firstinput terminal is coupled directly or indirectly with the secondcontroller terminal. The second input terminal is configured to receivea second voltage. The output terminal is coupled to the second capacitornot through any controller terminal. For example, the system controlleris implemented according to at least FIG. 2, FIG. 3, FIG. 4, FIG. 11,FIG. 12, and/or FIG. 14.

According to another embodiment, a system controller is provided forregulating a current flowing from a first controller terminal to asecond controller terminal. The system controller includes: a low passfilter configured to receive a current sensing signal related to thecurrent flowing from the first controller terminal to the secondcontroller terminal, the low pass filter being further configured togenerate a filtered signal based at least in part on the current sensingsignal; an error amplifier configured to receive the filtered signal anda first reference signal and generate a compensation signal based atleast in part on the filtered signal and the first reference signal, theerror amplifier including a capacitor; and a driver configured togenerate a drive signal based on at least information associated withthe compensation signal and output the drive signal to one or moreswitches to affect the current flowing from the first controllerterminal to the second controller terminal. The error amplifier furtherincludes a first input terminal, a second input terminal, and an outputterminal. The first input terminal is configured to receive the filteredsignal. The second input terminal is configured to receive the referencesignal. The output terminal is coupled directly to the capacitor. Forexample, the system controller is implemented according to at least FIG.3 and/or FIG. 4.

According to yet another embodiment, an error amplifier includes: atransconductance amplifier including a first input terminal and a secondinput terminal and a first output terminal, the first input terminalbeing configured to receive a first voltage signal, the second inputterminal being configured to receive a second voltage signal, the firstoutput terminal being configured to generate a current signal based atleast in part on the first voltage signal and the second voltage signal;a first switch including a first switch terminal and a second switchterminal and configured to be open or closed in response to a firstcontrol signal, the first switch terminal being coupled to the firstoutput terminal; a capacitor including a first capacitor terminal and asecond capacitor terminal, the first capacitor terminal being coupled tothe second switch terminal; an operational amplifier including a thirdinput terminal, a fourth input terminal, and a second output terminal,the third input terminal being coupled to the first capacitor terminal;and a second switch including a third switch terminal and a fourthswitch terminal, the third switch terminal being coupled to the secondoutput terminal, the fourth switch terminal being coupled to the firstoutput terminal, the second switch being configured to be open or closedin response to a second control signal. If the first control signal isat a first logic level, the second control signal is at a second logiclevel. If the first control signal is the second logic level, the secondcontrol signal is at the first logic level. The first logic level andthe second logic level are different. For example, the error amplifieris implemented according to at least FIG. 4.

In one embodiment, a system controller includes: a first controllerterminal configured to allow a first current to flow out of the systemcontroller through the first controller terminal to a resistorassociated with a resistance, the first controller terminal beingfurther configured to receive a voltage signal based at least in part onthe first current and the resistance, the resistor not being any part ofthe system controller. The system controller is configured to processthe received voltage signal, generate a clock signal associated with anoperating frequency based at least in part on the voltage signal, andchange the operating frequency based at least in part on the resistance.For example, the system controller is implemented according to at leastFIG. 6, FIG. 7, FIG. 8, and/or FIG. 9.

In another embodiment, a system controller is provided for regulating acurrent flowing through one or more light emitting diodes. The systemcontroller includes: a voltage-to-current converter configured toreceive a first voltage associated with a first controller terminal andgenerate a first current based at least in part on the first voltage,the first controller terminal being configured to provide a secondcurrent to a resistor for generating the first voltage; an oscillatorconfigured to receive the first current and generate a clock signalbased at least in part on the first current, the clock signal beingassociated with an operating frequency of the system controller; and adriver configured to generate a drive signal associated with theoperating frequency and output the drive signal to affect a thirdcurrent flowing through one or more light emitting diodes. Theoscillator is further configured to generate a ramp signal associatedwith an operating frequency based at least in part on the first current,the operating frequency corresponding to an operating period, theoperating period including a ramp-up period and a ramp-down period. Theoscillator is further configured to: ramp up the ramp signal from afirst magnitude to a second magnitude during the ramp-up period and rampdown the ramp signal from the second magnitude to the first magnitudeduring the ramp-down period, the first magnitude and the secondmagnitude being different; and adjust a duration of the ramp-down periodin response to a change of the voltage signal in magnitude. For example,the system controller is implemented according to at least FIG. 7 and/orFIG. 8.

In yet another embodiment, a system controller is provided forregulating a current flowing through one or more light emitting diodes.The system controller includes: an error amplifier configured to receivea first voltage related to a first current flowing out of a firstcontroller terminal and generate a second voltage based at least in parton the first voltage; a clock-signal generator configured to receive thesecond voltage and generate a clock signal based at least in part on thesecond voltage, the clock signal being associated with an operatingfrequency of the system controller; and a driver configured to generatea drive signal associated with the operating frequency and output thedrive signal to affect a second current flowing through one or morelight emitting diodes. The system controller is further configured to:keep the operating frequency unchanged at a first frequency magnitude inresponse to the second voltage changing if the second voltage remainssmaller than a first voltage magnitude; keep the operating frequencyunchanged at a second frequency magnitude in response to the secondvoltage changing if the second voltage remains larger than a secondvoltage magnitude; and change the operating frequency in response to thesecond voltage changing if the second voltage remains larger than thefirst voltage magnitude and smaller than the second voltage magnitude.The second voltage magnitude is larger than the first voltage magnitude.For example, the system controller is implemented according to at leastFIG. 12, and/or FIG. 13.

In yet another embodiment, a method is provided for regulating a currentflowing through one or more light emitting diodes. The method includes:receiving a first voltage related to a first current flowing out of afirst controller terminal; generating a second voltage based at least inpart on the first voltage; receiving the second voltage; generating aclock signal based at least in part on the second voltage, the clocksignal being associated with an operating frequency; generating a drivesignal associated with the operating frequency; and outputting the drivesignal to affect a second current flowing through one or more lightemitting diodes. Generating a clock signal based at least in part on thesecond voltage includes: keeping the operating frequency unchanged at afirst frequency magnitude in response to the second voltage changing ifthe second voltage remains smaller than a first voltage magnitude;keeping the operating frequency unchanged at a second frequencymagnitude in response to the second voltage changing if the secondvoltage remains larger than a second voltage magnitude; and changing theoperating frequency in response to the second voltage changing if thesecond voltage remains larger than the first voltage magnitude andsmaller than the second voltage magnitude. The second voltage magnitudeis larger than the first voltage magnitude. For example, the method isimplemented according to at least FIG. 12, and/or FIG. 13.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits. In yet anotherexample, various embodiments and/or examples of the present inventioncan be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

1-54. (canceled)
 55. A system controller comprising: a first controllerterminal configured to receive an input voltage, the first controllerterminal being further configured to allow a first current flowing intothe system controller based at least in part on the input voltage inresponse to one or more switches being closed; a second controllerterminal configured to allow the first current to flow out of the systemcontroller through the second controller terminal in response to the oneor more switches being closed, the second controller terminal beingfurther configured to receive a current sensing signal based at least inpart on the first current; a third controller terminal; a fourthcontroller terminal coupled to the third controller terminal through acapacitor, the capacitor not being any part of the system controller; anerror amplifier configured to generate a compensation signal based atleast in part on the current sensing signal; and a driver configured togenerate a drive signal based at least in part on the compensationsignal and output the drive signal to affect the first current flowingfrom the first controller terminal to the second controller terminal;wherein the fourth controller terminal is coupled to a clamping device.56. The system controller of claim 55 is located on a chip.
 57. Thesystem controller of claim 56 wherein: the first controller terminal isa first pin of the chip; the second controller terminal is a second pinof the chip; the third controller terminal is a third pin of the chip;and the fourth controller terminal is a fourth pin of the chip.
 58. Thesystem controller of claim 57 wherein the error amplifier and the driverboth are located on the chip.
 59. The system controller of claim 57wherein the capacitor is located off the chip.
 60. The system controllerof claim 57 wherein the one or more switches are located on the chip.61. The system controller of claim 55 wherein the one or more switchesare coupled between the first controller terminal and the secondcontroller terminal and are configured to close or open in response tothe drive signal.
 62. The system controller of claim 55, furthercomprising a fifth controller terminal configured to receive a feedbacksignal and detect a demagnetization process based at least in part onthe feedback signal.
 63. The system controller of claim 62 wherein thesystem controller includes no controller terminal other than the firstcontroller terminal, the second controller terminal, the thirdcontroller terminal, the fourth controller terminal, and the fifthcontroller terminal.
 64. The system controller of claim 55 wherein theone or more switches are one or more parts of the system controller. 65.A system controller for regulating a current flowing from a firstcontroller terminal to a second controller terminal, the systemcontroller comprising: a filter configured to receive a current sensingsignal related to the current flowing from the first controller terminalto the second controller terminal, the filter being further configuredto generate a filtered signal based at least in part on the currentsensing signal; an error amplifier configured to receive the filteredsignal and a first reference signal and generate a compensation signalbased at least in part on the filtered signal and the first referencesignal, the error amplifier including a capacitor; and a driverconfigured to generate a drive signal based on at least informationassociated with the compensation signal and output the drive signal toone or more switches to affect the current flowing from the firstcontroller terminal to the second controller terminal; wherein: the oneor more switches are coupled to the first controller terminal and thesecond controller terminal; and the one or more switches are configuredto allow the current to flow from the first controller terminal throughthe one or more switches to the second controller terminal in responseto the one or more switches being closed.
 66. The system controller ofclaim 65 is located on a chip.
 67. The system controller of claim 66wherein: each of the filter, the error amplifier, and the driver islocated on the chip; and the capacitor is located on the chip.
 68. Thesystem controller of claim 66 wherein the one or more switches arelocated on the chip.
 69. The system controller of claim 65, furthercomprising a feedback sensor configured to receive a feedback signal anddetect a demagnetization process based at least in part on the feedbacksignal.
 70. An error amplifier comprising: a transconductance amplifierincluding a first input terminal and a second input terminal and a firstoutput terminal; a first switch including a first switch terminal and asecond switch terminal and configured to be open or closed in responseto a first control signal, the first switch terminal being coupled tothe first output terminal, the second switch terminal being coupled to afirst capacitor terminal of a capacitor; an operational amplifierincluding a third input terminal, a fourth input terminal, and a secondoutput terminal, the third input terminal being coupled to the firstcapacitor terminal of the capacitor, the capacitor further including asecond capacitor terminal; and a second switch including a third switchterminal and a fourth switch terminal, the third switch terminal beingcoupled to the second output terminal, the fourth switch terminal beingcoupled to the first output terminal, the second switch being configuredto be open or closed in response to a second control signal; wherein: inresponse to the first control signal being at a first logic level, thesecond control signal is at a second logic level; in response to thefirst control signal being at the second logic level, the second controlsignal is at the first logic level; and the first logic level and thesecond logic level are different.
 71. The error amplifier of claim 70wherein the first switch terminal is coupled directly to the firstoutput terminal.
 72. The error amplifier of claim 70, furthercomprising: a resistor; wherein the second switch terminal is coupled tothe first capacitor terminal through the resistor.
 73. The erroramplifier of claim 70 wherein the third input terminal is coupleddirectly to the first capacitor terminal.
 74. The error amplifier ofclaim 70 wherein the third switch terminal is coupled directly to thesecond output terminal.
 75. The error amplifier of claim 70, furthercomprising: a resistor; wherein the fourth switch terminal is coupled tothe first output terminal through the resistor.
 76. The error amplifierof claim 70 wherein the first switch is configured to be open inresponse to the first control signal being at the first logic level andto be closed in response to the first control signal being at the secondlogic level.
 77. The error amplifier of claim 70 wherein the secondswitch is configured to be open in response to the second control signalbeing at the first logic level and to be closed in response to thesecond control signal being at the second logic level.